1. Field of the Invention
The present invention relates to an image freezing unit for obtaining a still image from image data obtained by an imaging means.
2. Related Art
Recently, an endoscopic imaging unit has been developed, in which there is provided a solid-state imaging element such as a CCD at the tip of an endoscope, and the inside of body cavity is illuminated sequentially with trichromatic lights of red, green and blue so as to image the inside in color, and then a diagnosis is pronounced on the basis of the color-image displayed on a monitor unit. In this method, it is required to image trichromatic component images in order to image a color image. Thus, it takes time and tends to cause color discrepancy on the image due to the accidental movement of an object or an operator's hand. In addition, in the event of observing a still image on the monitor unit, when a freeze command is executed to the endoscopic imaging unit, a freezing operation for the unit is unconditionally performed in accordance with the command to obtain a still image.
Therefore, when executing the freeze command while the object and the position of the endoscope tip move relatively, color discrepancy or image blurred on the still image occurs. Conventionally, for example, as shown in the official gazette of the Japanese provisional publication No. 212591/92, a freezing unit has been presented, wherein a still image with the least amount of color discrepancy can be obtained from images after a predetermined time has passed since the execution of freeze command.
Further, for example, as in the official gazette of the Japanese provisional publication No. 154100/93, a freezing unit has been presented, wherein whenever a desired scene is required to be frozen, a still image with a color discrepant magnitude below a predetermined value can be obtained without any perceived time delay.
Further, for example, in the official gazette of the Japanese provisional publication No. 279689/89, a freezing unit has been presented, wherein an image stored in a memory is compared after the freeze command is executed, so as to obtain a still image with the least amount of color discrepancy.
However, the freezing means in the publication No. 212591/92 described above provides an image with the least amount of color discrepancy after a predetermined time has passed since the execution of freeze command, so a time difference caused by the response time of an operator occurs between an image to be frozen and an image actually obtained.
Further, the color discrepancy preventive means in the publication No. 154100/93 described above provides a still image at a color discrepant magnitude below a determined value, so the image quality is unsatisfactory when compared with an image with the least color discrepancy, and a previous image may be output when the freeze command is executed while the image with the color discrepant magnitude below the determined value is not updated yet.
Further, the color discrepancy preventive means in the publication No. 279689/89 described above, detects an image with the least amount of color discrepant magnitude from images stored in a memory after the execution of the freeze command, so it takes time for evaluation, and there is a certain lag time until a still image is actually obtained.